(a) Field of the Invention
The present invention relates to a non-aqueous electrolyte and a secondary battery comprising the same.
(b) Description of the Related Art
Recently, the compact and lightweight construction of electronic equipment has been realized and the use of portable electronic devices has been generalized, and thus studies on secondary batteries having high energy density have been actively conducted.
Lithium secondary batteries, which are currently mainly used, comprise cathode and anode made of materials capable of intercalating and deintercalating lithium ions, are fabricated by injecting a non-aqueous electrolyte between the cathode and anode, and produce electrical energy by oxidation and reduction reactions, which occur when lithium ions are intercalated into and deintercalated from the cathode and anode.
However, such lithium secondary batteries have a disadvantage in that the non-aqueous electrolyte used therein may cause safety-related problems such as ignition and explosion, and such problems become severe as the capacity density of the batteries is increased. Specifically, when the batteries are overcharged past conventional operating voltage, the cathode will release an excess amount of lithium, which will produce dendrite on the anode. Thus, both the cathode and the anode will be thermally unstable so that a rapid exothermic reaction such as the decomposition of the electrolyte will occur. This exothermic reaction causes thermal runaway, which results in the ignition and explosion of the batteries, thus reducing the safety of the batteries.
Prior techniques proposed to solve the problems resulting from the overcharge of the lithium secondary batteries broadly include methods that use electronic circuits and methods that use chemical reactions.
The methods that use electronic circuits are methods of mechanically interrupting an electric current by promoting the generation of gas when the overcharge of the batteries takes place. These methods have problems in that high cost is incurred and various limitations arise in processes for designing and fabricating the batteries.
The methods that use chemical reactions include a method comprising fusing the separator to shutdown the pores of the separator, and a method in which an appropriate redox shuttle additive, i.e., an oxidation-reduction reagent that undergoes oxidation-reduction cycling, is added to the electrolyte. However, these methods have a problem in that the redox shuttle additive has a short cycle life.